Gate driver on array (GOA) technology is a technology of fabricating a gate drive circuit on an array substrate directly. The basic principle of the conventional GOA circuit is shown in FIG. 1. The shifting and switching of gate lines are generally realized by shift registers. The input ends of the shift registers include Voff, CKV, and CKVB. The input ends of a first stage shift register include a gate turn-off time signal Voff input end, a clock signal CKV input end, a reverse clock signal CKVB input end, and a start signal STVP input end. The output end of the first stage shift register is connected with a first stage gate line. The input ends of a second stage shift register (as well as all the shift registers after the second stage) include a Voff signal input end, a CKVB signal input end, and a STVP signal outputted by a former stage. The output end of the second stage shift register is connected with a second stage gate line. The signal outputted by the output end of the second stage shift register is also inputted to the first stage shift register as feedback signal. The connection principle of the subsequent stages is the same as above.
After a conventional thin film transistor liquid crystal display (TFT-LCD) is shut down, a phenomenon of shutdown afterimage occurs since there are residual charges in pixels on a liquid crystal display panel. In order to solve the problem of shutdown afterimage, an XON function circuit is generally employed, i.e., turning on all the thin film transistors (TFTs) at the moment of shutdown and switching on all the gate lines at the moment of shutdown, so as to enable the residual charges in the pixels to be released immediately. In this way, a display screen can recover to a white screen mode rapidly, thereby eliminating the shutdown afterimage. The timing of the XON signal which implements the XON function is shown in FIG. 2. FIG. 2 shows timing of a gate drive signal performing display normally and timing of an XON signal inputted when shutdown is carried out, wherein the XON signal can switch on all the TFTs simultaneously. FIG. 2 also shows a TFT panel, wherein a gate driver is connected laterally, and a source driver is connected longitudinally.
The conventional GOA basic circuit usually employs a 4T1C structure, the design of which is shown in FIG. 3. The circuit comprises four transistors (i.e., TFT1, TFT2, TFT3, and TFT4) and a capacitor Cb. The circuit further comprises a clock signal end CLK, a low level signal end Vss, and three output ends Output[N−1], Output[N], and Output[N+1]. There are mutual relations among respective gate lines in the conventional GOA circuit, i.e., at the time of turning on a next row of gate line, turning off the previous row of gate line. Assuming that an XON signal is used in the conventional GOA circuit in order to eliminate the shutdown afterimage, both the output end of the N−1th stage Output [N−1] and the output end of the N+1th stage Output [N+1] need to be connected with the high level XON signal, so as to enable both transistors TFT3 and TFT4 to be switched on. On the other hand, since the drain of the TFT3 is connected with a low level signal Vss, when both the TFT3 and TFT4 are switched on, the level at the output end of the N−1th stage Output[N−1] should be a low level. However, since the output end of the N−1th stage Output[N−1] has been connected with a high level XON signal, a level conflict will occur at the output end of the N−1th stage Output[N−1]. Moreover, since the output end of the N+1th stage Output[N+1] is connected with a high level XON signal, TFT2 is switched on, such that the output end of the Nth stage Output[N] outputs a low level, thereby enabling the Nth stage of gate lines to be turned off, and the function of the XON signal for enabling all the gate lines to be switched on cannot be implemented. Therefore, the XON signal cannot be used in the conventional GOA circuit.
As a result, the conventional GOA circuit cannot switch on all the gate lines during shutdown as the XON signal cannot be used. Hence, the influence of shutdown afterimage cannot be eliminated in this manner.